The present invention relates to a unidirectional mechanism useful in electrical disconnects and in particular to a unidirectional mechanism providing smooth rotation and high strength.
Referring to FIG. 1, a disconnect in the form of a standard fuse block 10 of the prior art may receive fuse cartridges 12 along its front face and may attach at its rear face to the rear wall 14 of a metal cabinet 16.
Input terminals along the top of fuse block 10 may receive wires 18 which connect independently to one side of each fuse cartridge 12, the latter which interconnect wires 18 to wires 20 attached to output terminals along the bottom of the fuse cartridge 12. Wires 18, for example, may be connected to a source of three-phase power and wires 20, for example, may be connected to a motor or other piece of equipment.
Fuse block 10 may be activated to electrically disconnect wires 18 from the respective fuse cartridges 12. The fuse block 10 may be controlled by a rotary shaft 22 along one side of the fuse block 10 and extending in an orientation perpendicular to the rear wall 14 of cabinet 16 toward an open face of the cabinet.
The open face of the cabinet may be covered by a door 24 attached by hinges to one side of the cabinet 16. Door 24 may support a captively mounted rotary knob 26 having an inwardly extending connector 28.
Referring now to FIG. 2, knob 26 may include connector 28 that extends inwardly through an opening in the door 24. Connector 28 includes retaining flanges 30 for retaining it rotatably within that opening.
When door 24 is closed about the cabinet 16, connector 28 of the knob 26 engages the outermost end of rotary shaft 22, thereby allowing rotary shaft 22 to be operated by knob 26 when door 24 is closed on cabinet 16. Specifically, an inwardly facing end of connector 28 may include a keyway 32 receiving a rectangular end of rotary shaft 22 and a pin 34 extending perpendicularly through the rotary operator. Turning knob 26, in turn, rotates shaft 22 to electrically disconnect or connect power to wires 20.
Referring again to FIG. 1, knob 26 allows disconnection of power to wires 20 when the door 24 on the cabinet 16 is closed. However, when door 24 is open, rotary shaft 22 is exposed, thereby enabling power to be inadvertently reconnected by counter rotation the shaft 22.
One apparatus for preventing the reconnection of power while the door is open includes a mechanism that is connected to the exterior of fuse block 10 as described in U.S. Pat. No. 6,700,081, entitled “Fuse Block With Door Sensing Rotary Disconnect” assigned to the assignee of the present invention and hereby incorporated by reference. The mechanism enables knob rotation to connect and disconnect the power when the door is closed, and further prevents inadvertent counter rotation of the knob to reconnect the power when the door is open. While this apparatus is suitable for its intended purpose, the mechanism requires modification of an existing fuse block.
U.S. Pat. No. 6,881,909, entitled: “Fuse Block With Integral Door Sensing Rotary Disconnect” also assigned to the assignee of the present invention and hereby incorporated by reference, describes a handle, accessible within the door, is open and incorporating a uni-directional mechanism that allows disconnecting of power by turning the handle, and the block reconnecting of power by turning the handle in the opposite direction until a secondary operation of pulling the handle out is performed.
The unidirectional mechanism employed in the above inventions uses a set of pawl teeth that engage a slotted disk. U.S. Application 2005/0040019 entitled: “Fuse Block with Integral Door Sensing Rotary Disconnect”, also assigned to the assignee of the present invention and hereby incorporated by reference, describes a unidirectional mechanism employing balls fitting between a scalloped track and inner drive providing smooth relative rotation between the drive and the track in one direction, and a positive rotational locking of the drive in the other direction.